Even in a democracy,there are restrictions on what a person can do, If you want to test this take a public domain TV ad film made by a rich and powerful corporation. Now remake it and PUBLISH this new film which now declates that the corporation ,s product is total harmful rubbish. Good luck

Well, if you re-edit a multi-national corporation's TV ad, of course they will sue you. That would be a civil action, and has nothing to do with your free speech rights. You still had the fair use right to edit their ad for commentary and criticism as part of U.S. copyright law. The fair use provision of that law would be your defense in the lawsuit.

Aha, the key! Go ahead and twist and distort the statements of the poor and powerless! They won't sue, so they can be abused forever! But dare anyone re-edit the statements of the rich and powerful into something unacceptable you will burn in legal hell!